Move shebang detection into classifier

Fixes #203

samples/JavaScript/js2.script!

@@ -0,0 +1,7 @@
+#!/usr/bin/env node
+var http = require('http');
+http.createServer(function (req, res) {
+  res.writeHead(200, {'Content-Type': 'text/plain'});
+  res.end('Hello World\n');
+}).listen(1337, '127.0.0.1');
+console.log('Server running at http://127.0.0.1:1337/');